Lymphocyte

A type of white blood cell (leucocyte), present in blood, the lymph nodes, spleen, thymus gland, gut wall, and bone marrow. Lymphocytes provide immunity and occur in two forms: B-lymphocytes, the agents of the humoral immune system, which recognize antigens and produce specific antibodies against them; and T-lymphocytes, the agents of cell-mediated immune system, which secrete immunologically active compounds and assist B cells in their function. T-lymphocytes can differentiate into helper, killer, or suppressor cells.